Semiconductor device manufacturing: process – Having organic semiconductive component
Reexamination Certificate
2002-07-25
2004-04-06
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Having organic semiconductive component
C438S029000, C257S040000, C257S103000
Reexamination Certificate
active
06716662
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Application No. 2001-261619 filed in Aug. 30, 2001, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a production method for an organic electroluminescent device, an electroluminescent device produced by such a production method, and an organic electroluminescent display panel employing such an organic electroluminescent device.
2. Description of the Related Art
Organic electroluminescent devices (organic EL devices) are light emitting devices typically including a first electrode, an organic film comprising at least a light emitting layer, and a second electrode, which are stacked in this order on a substrate. In recent years, the organic EL devices, which are expected to be applied to display panels, have been under intensive studies in various fields.
When a voltage is applied between the first and second electrodes of the organic EL device, electrons are injected into the light emitting layer of the organic film from one of the electrodes, and holes are injected into the light emitting layer from the other electrode. Thus, the electrons are coupled with the holes to provide facial light emission from the light emitting layer.
To provide the facial light emission, it is desirable that one of the electrodes is transparent. In most cases, a transparent substrate is employed as the substrate, and a transparent electrode film is formed as the fist electrode on the transparent substrate, so that the light emission can be outputted from the side of the first electrode. That is, the organic EL device includes the transparent first electrode, the organic film including at least the light emitting layer, and the transparent or non-transparent second electrode, which are stacked in this order on the transparent substrate.
A reason why the light emission is outputted from the first electrode side in the conventional organic EL device is that a glass substrate formed with an ITO conductive film for general use in a liquid crystal display panel and the like is used as the substrate for the organic EL device. The term “ITO” stands for tin indium oxide, and the ITO film is generally employed as a transparent electrode.
The recent research and development is directed to an organic EL device which is adapted to output light emission from a second electrode side opposite from a substrate thereof for improvement of the characteristics and efficiencies of the organic EL device. More specifically, the organic EL device includes a transparent or non-transparent first electrode, an organic film comprising at least a light emitting layer, and a transparent second electrode, which are stacked in this order on a transparent or non-transparent substrate, so that facial light emission from the light emitting layer is outputted through the transparent second electrode.
This arrangement leads to improvement in light emitting efficiency and reduction in power consumption, because a loss in light emission can be suppressed which may otherwise occur due to reflection on the substrate in the case of the conventional device adapted to output the light emission from the first electrode side.
In addition, there is a wide choice of materials for the substrate. That is, a non-transparent substrate such as a ceramic substrate or a silicon substrate can be employed.
Where a display panel incorporating organic EL devices in pixel light emitting sections thereof is driven by TFTs (thin film transistors), the aperture ratio of the display panel is advantageously improved.
With reference to
FIGS. 5
to
7
, an explanation will be given to the construction of the organic EL display panel which includes conventional organic EL devices adapted to output light emission from a second electrode side, and to a production method therefor.
FIG. 5
is an explanatory diagram schematically illustrating the construction of the organic EL display panel (organic EL display) which includes the conventional organic EL devices adapted to output the light emission from the second electrode side.
FIG. 6
is a diagram for explaining the step of forming organic films on first electrodes of the conventional organic EL devices shown in
FIG. 5
by a transfer method, and
FIG. 7
is a diagram for explaining the step of forming second electrodes on the transferred organic films.
The conventional organic EL display panel
110
shown in
FIG. 5
includes organic EL devices
110
a
,
110
b
,
110
c
. The organic EL devices
110
a
,
110
b
,
110
c
each include a common substrate
101
, a first electrode
102
, an organic film
103
comprising at least a light emitting layer, and a second electrode
105
.
For production of the organic EL display panel
110
, the first electrode
102
and the second electrode
105
are each formed in a predetermined pattern. Where the organic EL display panel is of a full color type, the organic films
103
of the respective organic EL devices
110
a
,
110
b
and
110
c
should be formed separately for red (R), green (G) and blue (B) light emission.
The substrate
101
and the first electrodes
102
of the conventional organic EL devices
110
a
,
110
b
,
110
c
are not required to be transparent, but at least the second electrodes
105
on the respective organic films
103
are required to be transparent, because the light emission is outputted from the side of the second electrodes
105
.
The formation of the organic films
103
on the first electrodes
102
is achieved by a known method such as an evaporation method, a spin coating method, a printing method, a laminating method or an ink jet method. In recent years, a transfer method has attracted attention.
In the transfer method, a donor film is prepared by forming a thin film (an organic film to be transferred onto the first electrode) on a base film such as a PET (polyethylene terephthalate) film by an evaporation method, a spin coating method or a sputtering method. The donor film is applied onto the substrate, and irradiated with an energy such as a laser beam or heat from the side of the base film thereof, whereby irradiated portions of the thin film are transferred onto the substrate (see, for example, Japanese Unexamined Patent Publications No. 9(1997)-167684 and No. 10(1998)-208881).
The base film is not limited to the aforesaid PET film but, where a laser beam is employed as a heat source, a PET film formed with a light-to-heat conversion layer and a heat conduction layer is preferably used.
An advantage of the transfer method is that layers of the thin film stacked on the base film are transferred onto the substrate as they are in a reverse stacking order. Therefore, the layers of the thin film (layers of the organic film) can collectively be formed on the substrate.
Further, there is no need to pattern the thin film on the base film, but it is merely necessary to form the thin film on the entire base film.
Since only the portions of the thin film irradiated with the laser beam or the heat are transferred from the donor film onto the substrate, the organic film can be formed in a highly precise pattern on the substrate without the use of a shadow mask as employed in the evaporation method. For example, the transfer method can easily form a line pattern having a width of 200 &mgr;m or smaller. Therefore, a more precise organic EL display panel can more easily be produced than in the case where the conventional shadow mask is employed.
For the aforesaid reasons, the transfer method is advantageous for the production of the organic EL display panel.
With reference to
FIG. 6
, a more specific explanation will be given to the step of forming the organic films
103
of the conventional organic EL devices
110
a
,
110
b
,
110
c
shown in
FIG. 5
by the transfer method.
As shown in
FIG. 6
, a donor film
210
including an organic film
103
provided over a base film
204
and comprising at least a light emitting
Elms Richard
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
Wilson Christian D.
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